https://www.scalemates.com/products/reviews.php?scale=1%3A232&topic=Cruiser+USS+Olympia
Scalemates is pretty useful, by no means always up to date.
In the case of the Olympia there's only been a couple of plastic models. Anything made for the Pyro would not work for the Encore, and vice versa. The Pyro is grossly inaccurate too.
I don't think you'll find any aftermarket parts for the Encore model, as they also make a set of their own and it wouldn't be economical for anyone else to try to compete with them
But write Squadron and ask them, they might have it separate.
EDIT: KA made the decks for Encore. I don't see it listed on the KA website. Artwox made one too, but everywhere I looked its "out of stock".